Recently, use of various pieces of content using terminal devices such as a personal computer (PC) or a mobile phone (smart phone) which a user possesses has spread. Examples of the pieces of content include electronic books described in Patent Literature 1 and moving image content distributed through a network. Technology for adding additional information to content and providing the content has been suggested. For example, technology for adding metadata to an electronic book and displaying information associated with an information item included in the electronic book has been suggested in Patent Literature 1.